METHOD FOR TAKING REAL EXPANSION RATIO LARGER THAN REAL COMPRESSION RATIO IN FOUR-CYCLE ENGINE

摘要

PROBLEM TO BE SOLVED: To improve the engine output while setting the expansion ratio larger than the compression ratio by providing a four-cycle engine with a valve to be opened at a bottom dead center in a compression stroke and to be closed in an expansion stroke before the air-fuel mixture is excessively expanded by explosion and resists the rotation. SOLUTION: A cylinder head of a four-cycle engine is provided with an intake valve 1, an exhaust valve 2, and a valve to be opened at a bottom dead center in the compression stroke and to be closed in the expansion stroke before the air-fuel mixture (or air) is excessively expanded by explosion and resists the rotation. At the time of compression stroke, the force for extruding the air-fuel mixture from inside of the cylinder is converted to the force for pushing the air-fuel mixture into the cylinder so as to improve the output. A vacant part 8 for temporarily storing the air-fuel mixture is provided in a passage 7 formed from the valve 3 to the intake pipe 5, and with this structure, a shock to be generated when the air-fuel mixture is discharged into the intake pipe 5 is relaxed so as to secure the safety operation.